Existing knowledge about neurologic conditions has been greatly enhanced by studies from Olmsted County, Minnesota, a naturally-occurring epidemiological experiment. This "community laboratory" is due to a) the relatively stable population, b) the accessibility of medical records since early in this century, and c) the limited number of health care providers in the area. Twenty years of intensive effort by the Principal Investigator have resulted in a facility which supports descriptive and analytic studies in the neurosciences. We now seek funding to continue the productively and applicability of this unique resource. This request for renewal of the Neuroepidemiology Program Project includes proposals covering 14 distinct topics in neurology. The studies will be a) descriptive in nature, providing incidence, prevalence, mortality and survivorship data; b) analytic in design, being either hypothesis-generating or hypothesis-testing or both; and c) of medicolegal and economic interest, with application to health care utilization issues. New efforts will include descriptive data for mental retardation, cervical radiculopathy, brain injury, trigeminal and glossopharyngeal neuralgia, and childhood spinal muscular atrophy. Case-control studies of carpal tunnel syndrome, Bell's palsy, cerebral palsy, mental retardation, brain tumors, and anorexia nervosa are proposed. Studies with other applications include the examination of the incidence rates and trends of neurosurgical and otolaryngological procedures, and etiologic and survivorship aspects of cerebral palsy. The medicolegal aspects of neurologic conditions necessitate reliable and valid epidemiologic data; estimates of the current burden, to the individual and to society, of neurologic illness and subsequent disability, require accurate data on the frequency, nature and severity of these conditions. Previous experience attests to the unparalleled contribution, in this respect, of studies from the Rochester Epidemiology Program Project (REPP) records-linkage system.